To explore the nature of existing racial/ethnic and socioeconomic disparities in health and identify the mechanisms by which they occur, more studies of diverse populations are being conducted in aging research. This research depends on a variety of self-report measures of health, health care, and psychosocial, cultural, socioeconomic, and environmental factors. To conduct large-scale research that include multiple racial, ethnic and SES groups and to be able to compare scores across these groups, we need to know that measures developed in mainstream, well-educated samples are conceptually and psychometrically equivalent when applied to these diverse population segments. Without such assurances, group comparisons may result in spurious results that negatively impact policy decisions. Currently, very little is known about how well existing measures work across these diverse groups, and few researchers in the U.S. are aware of the importance of this information. Our measurement core has been working on these issues for the past 5 years. We propose to continue to support health disparities and minority aging research by advancing development of conceptual frameworks of multi-level determinants of health disparities in older adults, empirically testing possible mechanisms for the disparities, including socioeconomic status, experiences of discrimination and/or racism, and sociocultural factors. We will advance development of environmental-level measures such as neighborhood resources. We will test the measurement invariance of the CES-D and the SF36 across racial/ethnic, age, and gender groups. Finally, we plan to enhance the awareness of researchers and policy makers of the importance of measurement studies in minority aging research, and increase their skills to conduct and interpret measurement analyses. To continue to advance the field, we will take the lead in designing and hosting a second RCMAR measurement conference in the year 2006 (year 4) with the goal of convening U.S. researchers to disseminate current knowledge in measurement and methods in health disparities and minority aging research. These proposed tasks will help us to continue to contribute toward assuring that the national goals to reduce health disparities can be met.